Aromatic azomethines

ABSTRACT

Novel azomethines are obtained when reacting a tertiary amine with an aromatic aldehyde or ketone having in orthoposition an activated methoxy group. These azomethines are capable of ring closure to yield a benzofurane and said tertiary amine. The benzofuranes are optical brighteners tranquilizers or intermediates for optical brighteners, fluorescent dyestuffs, scintiallators, sensibilizers for electrophotographic coatings.

United States Patent Sahm July 1, 1075 [54] AROMATIC AZOMETHINES 3,830,848 8/1974 Siegrist 260/566 F X [75] Inventor: Wilfried Sahm, Kelkheim, Taunus,

ermany Primary ExaminerGera1d A. Schwartz [73] Assignee: Hoechst Aktiengesellschaft, Attorney, Agent, or Firm-Connolly and Hutz Frankfurt am Main, Germany [22] Filed: Dec. 13, 1973 [21] App]. No.: 427,016 57 ABSTRACT [30] Foreign Application Priority Data Novel azomethines are obtained when reacting a ter- Dec 18, 1972 Switzerland 18397/72 tiary mine with an aromatic aldehyde Or ketone ing in orthoposition an activated methoxy group. [52] U.S. Cl. 260/566 F; 260/240 CA; 260/240 D; These azomethines are capable of ring closure to yield 2 0/24O 260/307 1 260/346 2 R; a benzofurane and said tertiary amine. The benzofu- 2 0/56 260/999 ranes are optical brighteners tranquilizers or interme- [51] Int. Cl. C07c 119/00 diates for Optical brighteners, fluorescent dyestuffs, 58 Field of Search 260/566 F, 566 R scintiallators, Sensibilizers for electrophotographic coatings. [56] References Cited UNITED STATES PATENTS 11/1973 Surrey 260/566 F X 5 Claims, N0 Drawings AROMATIC AZOMETHINES The present invention relates to the preparation of furan compounds.

It has been proposed to prepare compounds of the general formula (1 wherein A represents an aromatic monoor polynuclear ring system which is condensed with the furan nucleus by two adjacent carbon atoms as indicated, R represents a hydrogen atom, an optionally substituted molecular alkyl group of l to 4 carbon atoms or an optionally substituted phenyl group and D represents an organic radical being conjugated with the furan radical, by splitting off water, using a strongly basic condensating agent, from a compound of the formula (2) wherein A and R are defined as above and D represents an organic radical which is conjugated with the double bonds of the furan nucleus after ring closure (United States Pat. application Ser. No. 279,645).

The present invention provides a process for the preparation of compounds of the general formula (1), which comprises preparing compounds of the general formula (4) CR N-E A DKO/CHZ-D' from compounds of the general formula (2) and from amines of the general formula (3) E NH The azomethines of the general formula (4) are pre- 6 pared in a manner known per se at ambient or elevated temperature and, optionally, using solvents or diluents, for example, by heating them in toluene, chlorobenzene or other aromatic solvents, optionally in the presonce of an acidic catalyst, such as a mineral acid or a 6 substituted products of these aromatic amines or as an aliphatic amine the tertiary butyl amine. As these amines are split off during the reaction, the presence of substituents is, generally not advantageous in this case. However, for example amines of the general formula by the intramolecular ringclosure of a compound of the general formula (4) 05:)! I v- A ca B Y in strongly polar organic solvents under the action of strongly alkaline condensating agents.

The compounds of the general formula (4') are synthesized by reacting compounds of the general formula with aniline according to the process mentioned above. In the general formulae (1') and (2') and (4'), A is defined as above. The other symbols are defined as follows:

B represents a direct bond or a continuously conjugated chain of carbon atoms, which is, wholly or in part, a constituent of a carbocylic or heterocylic ring system in which one or more than one carbon atoms may be replaced by hetero atoms, especially a nitrogen atom, and the double bonds are placed in such a manner that the molecule is completely conjugated;

B is a direct bond or a continuously conjugated chain of carbon atoms which is, wholly or in part, a constituent of a carbocylic or heterocylic ring system in which one or more than one carbon atoms may be replaced by hetero atoms, especially by a nitrogen atom, and the double bonds are placed in such a manner that' a molecule, which is completely conjuv sulpho group, an acyl, sulphonyl or nitro group, or if e B contains an aromatic ring, also a hydrogen atom.

One or more substituents Y may be bound to the carboor heterocyclic ring systems of B and B, but also further halogen atoms, especially chlorine atoms. Alkyl and/or alkoxy groups, especially lower alkyl and/or alkoxy groups may also be linked to B, and accordingly to B, but only if B possesses electron-accepting groups. the electori-accepting influence of which on the CH group overcompensates the effect of the said groups as electron-donors.

Suitable substituents which may be linked to A'are of course only those which do not hamper norheavily disturb the reaction. Halogen atoms, alkyl, alkylene, aryl and alkoxy groups are preferred. But, alkenyl, alkinyl, aralkyl, aralkenyl, aralkinyl, optionally modified carboxy or sulfo groups, aryl, and sulfonyl groups may also be linked to A. Suitable substituents are especially those which contain aliphatic radicals having one to four carbon atoms and as aryl radical a phenyl radical. All substituents are not allowed to carry hydrogen atoms which can be replaced by metal atoms in a more easy or similarly easy manner as compared with the hydrogen atoms of the CH -group in the formulae (4),

(4') o r 'the following formula (4").

Functionally modified carboxy groups are, firstly, their salts with colourless cations, alkali metal ions or ammonium ions being preferred. there may, furthermore, be mentioned, the cyano group (nitrile group),

the carboxylate group or the carboxylic acid amide group. Carboxylate groups are especially those of the general formula COOR, wherein R is a phenyl radical or a lower alkyl group optionally having a branched chain, which radicals may contain further substituents, for example, a preferably lowmolecular dialkylamine, lowertrialkylammonium or alkoxy group in which dialkylamino or trialkylammonium groups two alkyl groups may be replaced by a ring, such as is in the morpholino or piperidino groups. A carboxylic acid amide group is especially one of the formula CONR R wherein the radicals R and R each represents a hydrogen atom or a lower alkyl group which may be, optionally, substituted, which may also form together with the nitrogen atom a hydroaromatic ring, which optionally, may carry further hetero atoms, such as oxygen or nitrogen atoms. for example, a piperidino or morpholino group.

Functionally modified sulpho groups are, by analogy with the description given above, the salts with colourless cations, preferably alkali metal ions or ammonium ions, and derivatives in which the SO -group is linked toa hetero atom, as to be found in the sulphonate group and in the sulphonamide group. Asulphonate trialkyl ammonium, acylamino (each as defined above) or sulpho group.

The present invention also provides a process for preparing a compound of the general formula (1) which comprises splitting off amine from compounds of the general formula (4") Al c.

The precusors (2), (2') and (2") are reaction products of compounds of the general formula (5) in which M represents an alkali metal or an alkaline earth metal cation and A and R are as defined in the general formula (1), with compounds fo the general formula (6), (6') or (6") in'each of which X represents a radical which can easily be split off as anion, preferably the anion of an inorganic acid-,preferably of a hydrohalic acid and D, B, and Y are as=defined in the general formula (2) and (2), in an organic solvent.

The alkali metal or alkaline earth metal salts (5) may, for example, be the following: Salicylic aldehyde, 5 chloro-salicylic aldehyde, 3,5-dichloro-salicylic aldehyde, 3-bromosalicylic aldehyde, 4-bromo-salicylic aldehyde, S-bromosalicyclic aldehyde, 3,5- dibromosalicylic aldehyde, 3-fluoro-salicylic aldehyde, 3-chloro-salicylic aldehyde, o-methyl-salicylic aldehyde, 5-chloro-6-methylsalicylic aldehyde, 3-methylsalicylic aldehyde, S-methylsalicylic aldehyde, 4-methyl-salicylic aldehyde, 5-chloro-4-methyl-salicylic aldehyde, 6-ethyl'salicylic aldehyde, 4-ethyl-salicylic aldehyde, 3,5-dimethyl-salicylic aldehyde, 4,5-dimethylsalicylic aldehyde, 3-phenyl-salicylic aldehyde or S-phenyl-salicylic aldehyde, Z-hydroxy-acetophenone, 2-hydroxy-4-chloro-acetophenone, Z-hydroxybenzophenone, 2-hydroxy-4,S-dimethyl-acetophenone or 2-hydroxy(oz-methoxy)-acetophenone.

As compounds of the general formula (6), (6) and (6") there may be mentioned, for example, thefollowing substances: benzylchloride, p-cyanobenzylchloride, p-carbomethoxy-benzylchloride, p-nitro-benzylchloride, p-trifluoromethylbenzylchloride, otrifluoromethyl-benzylchloride, 2,3,4,5,6-pentafluoro benzylchloride, mtrifluoromethyl benzylchloride, 4-bromomethyl benzosulphonic acid-dimethylamide, 2-chloromethyl-4- nitrophenol, 4-chloromethyl-a-phenyl-anisol, 5- bromoethyl-3-(4-tolyl)-1,2,4-oxadiazole, 5-bromopentadiene-( 1,3), l-cyano-5-chloro-pentadiene-( 1,3); cinnamyl chloride, cinnamyl bromide, 1,1-dipheny1-2- bromo methyl-ethylene, 2-bromoethyl-benzofuran, 3-bromomethyl-benzofuran, 3-bromomethylthiophene, 4,4'-bischloromethyl-diphenyl, 4,4-bischloromethyl-diphenyl ether, 2-bromomethyl4,5-benzo-benzofuran, 2-chloromethyl-benzoxazole, 5-chlorol-( 2-benzoxazolyl)-pentadiene-( 1,3), 2-chloromethyl- 4,5-benzo-benzoxazole, 2-chloromethyl-5,6-benzobenzoxazole, 2-chloromethyl-6,7-benzo-benzoxazole, Z-chloromethyl-5-methyl-benzoxazole, 2- chloromethyl-S,o-dimethyl-benzoxazole, 2- bromomethyl 5-carbomethoxy-furan, Z-bromomethyl- S-cyanofuran, 2-bromomethyl-5-carbomethoxythiophene, 2-bromomethyl-5-cyano-thiphene, 2- chloromethyl-pyridine, 3-chloromethyl-pyridine, 4- chloromethyl-pyridine, 2-chloromethyl-quinoline, lbromo-methyl-4-cyano-naphthalene, l-bromomethyl- 4-carbomethoxy-naphthalene and chloroacetonitrile.

lntermediates of the formula (4) which can be prepared according to the invention are, for example, the following:

cum-c ca 3 3 The ring closure reaction of the invention is carried out in strongly polar, neutral to alkaline organic solvents which are free form atoms capable of being replaced by alkali metals, especially hydrogen atoms. There may be used, for example, as solvents alkylated acyl amides of the general formula (8) wherein Alk is a lower alkyl group having not more than four carbon atoms, Acyl is the radical of a lowmolecular carboxylic acid having not more than four carbon atoms, especially formic acid and acetic acid, or the phosphoric acid radical, w indicates the basicity of the acid, i.e., how many base equivalents the acid can bind, and v is zero or the numbers 1 or 2, preferably 1 or 2, especially 2.

The following solvents may, for example, also suitably be used: tetramethyl urea, N-methyl-pyrrolidone, acetonitrile or pyridine.

The solvents, however which are of the general formula (7) are especially important, among which those are preferred in which v is 2. Dimethyl formamide, hexamethylphosphoric acid trisamide, diethylformamide and dimethylacetamide are of special interest.

The solvents can be used separately or in admixture with one another.

For the condensation reaction, strongly basic condensation agents are required, which are, for example, the strongly basic alkaline earth metals and especially alkali metal compounds, for example, the hydroxides, amides, hydrides, sulphides, alcoholates and strongly basic ion exchangers thereof, and further aluminum hydride, nitride or alcoholates.

The alcoholates to be used are especially derived from linear-chain, branched-chain or cyclic lower aliphatic alcohols having up to eight carbon atoms, preferably from linear-chain alkanols having from one to four carbon atoms.

The sodium or potassium compounds are preferably used, the hydroxides, amides and alcoholates thereof The compounds of the general formula 1 which can be prepared by the reaction described above are optical brighteners or if nitro groups are present precursors of brighteners which may be transformed to are ofspecial interest in practice. Mixture thereof may, brighteners by reduction of the nitro group to the of course, also be used. amino group, e.g. by catalytic hydrogenation.

The alkaline Condensation agehts are Preferably used They are also valuable intermediate products for a in at least the equivalent amount, but also, if necesary, v i f syntheses, f l for the preparation of a y times equivalent amount may he used P dyestuffs, scintillators and pharmaceutical products Ciany if the Compounds to be eohdeheated eohtahl 10 and for electrophotographic coatings. Optical brightengl'oups capable of being hydmhzed or it higher p ers of this type are known, for example, from German atures are required in which case part of the condensaoff l h ift Nos. 2 031 774 d 2 105 305 tioh agent y be consumed y reaction with the pharmaceutical products, for example, from US. Pat. Veht- No. 3,470,192.

when the Starting Compounds to be eohdehsated The following examples illustrate the invention: contain radicals sensitive to hydrolysis, for example, carboxylic acid ester groups, condensation products E X A M P L E 1 are isolated, especially at high reaction temperatures, 2L1 g f bi f h dib l were in which these groups are Present in hydrolysed State, heated to the boil with 4.7 g of aniline and 0.05 g of for example, the free eatboxylic acids or the cone 2O p-toluene-sulfonic acid in 250 ml oftoluene for2hours Spending Salts thereof, depending Oh the method of and the water was separated via a water separator. The working up. mixture was then allowed to cool, the precipitate which The Process of the hwehtloh has the special advanhad formed, was suction-filtered, washed with methag that Working is usually Possible at Smooth reaction no] and dried at 60C in vacuo. 27.1 g of the compound conditions. Reaction temperatures above 150C are 0 f the f l not necessary, temperatures above 120C are only required in exceptional cases.

Frequently, the reaction is carried out at room tem- (101 perature without external heating, which especially occurs when using potassium alcoholates or potassium hydroxide. In some cases it is advantageous or even CH=N @rhc" necessary to heat the reaction mixture which is advantageously covered by nitrogen, slowly to 30 120C @1 jg and to maintain that temperature for a certain time. ,6 ca

The essential advantage of the process of the inveno z 0 tion is that its reaction can easily be carried out and that almost quantitative yields are obtained especially also in those cases in which the formation of carbanions were b i d h i a l i point of 220 222C is not especially activated, for example in the Case Of (after recrystallization from dimethylformamide). compounds of the genera formula In manner analogous to that of compound 101 the The reaction product can be isolated fro the reaC- azomethines characterized in the following table 1 may tion mixture according to usual methods known per se. b th i d,

TABLE I No. in Constitution Melting point Solvent sequence CH :CH=N- (102) 0/0420 l-l97 DMF e (103) a 168-165 DMF CH 0 TQ 2 CH CH=N (104) m 172.5 DMF CH 3 o /CH TABLE I-Continued I No. in Constitution Melting point Solvent sequence 6C cum-Q l l (106) (mm-Q 176-180 DMF (CH 3 c CH w-G 107) a rcsiniC. not crystalline (10s) g Q fair gielllow O O from n- 0 CH c N butanol l25-l25.5 from no CH CH=CH butanol 132-134 crude (lll) l product (crude I product) CH O D (llZ) TABLE I Continued No. in Constitution Melting point Solvent sequence C CH=N- Q-Cl (112a) @K 167-169 (ll2b) 160-163 Cl (H26) 6 179-181 An isolation of the intermediate or purification of the azomethines is generally, however, not necessary. Preferably, the solvents used for the preparation of the azomethines are distilled off in vacuo, then replaced by a suitable dipolar solvent and the ring closure reactions described in Examples 2 to 6 are immediately carried out.

EXAMPLE 2 were obtained which had a melting point of l37l39C.

The compound was purified by recrystallization from gasoline (melting range: lOOl50C) and then had a melting point of l4l.5l42.5C.

EXAMPLE 3 65 57.2 g of the compound lOl were suspended in 400 ml of dimethyl formamide, 12.55g of potassium hydroxide (pulverized, about 90 were added and the reaction mixture was slowly heated to 100 120C. This temperature was maintained for 3 hours. Then the batch was allowed to cool to room temperature and the precipitate which had formed, was suctionfiltered. The filter residue was washed with dimethyl formamide, then with water until it became neutral and then dried at 60C in vacuo. 36 g of crude product of the formula (1 l4) 5@LU-@-@U@W were obtained which could be purified by recrystallization from a-chloronaphthalene.

Melting point: 350C. C H O Calculated: C 87.9, H, 4.79 (386.45)

Found: 87.7, H 4.80 Amax. (absorption/DMF): 351 nm, e 7.06 lO EXAMPLE 4 36.3 g of the compound (110) were dissolved in 400 ml of N,N-dimethylacetamide, 12.2 g of potassium tertiary butylate were added and the mixture was heated to 8090C for 2 hours while stirring. After cooling, it was worked up as described in example 2. 26 g of crude product of the formula (1 15) were obtained which could be purified by recrystallization from n-butanol while adding active charcoal. Melting point: l76l77C.

EXAMPLE 5 were obtained, which were recrystallized from dimethyl formamide with the addition of active charcoal. Melting point: 308-309C EXAMPLE 6 37.7 g of the compound 1 12) were dissolved in 400 ml of hexamethyl-phosphoric acid trisamide and 7 g of sodium hydroxide were added. The mixture was stirred at 60C for 2 hours and working up followed as described in example 2. So, 25 g of crude product of the formula 1 l7) l l l l:

were obtained which had a melting point of 171C.

In a manner analogous to that described in the precedmg examples the compounds listed in the following table, were prepared.

TABLE 2 No. in Constitution Melting Solvent alkali reaction sequence point metal temperature "C compound "C i l 18 r l73 l75 DEF NaOH 4O l l. c n

l l) 218-220 DMF KOH 25 130 1244 DMF KOH 100 [2] 199-200 HMPT KOH 25 122 -"0C N l2o-l1t DMA KOH Z5 [23 m fl -CO 1143 DMF KO-tert.- 25

-' butylate TABLE 2 Continued,

No. in Constitution Melting Solvent alkali reaction sequence point metal temperature "C compound C CH 124 3 -36 DMF KO-terL- 1.20

lo 1 butylate 125 I 222423 DMF I NaOH O Q c0011 CH3 126 I CEN 195 DMF NaOH 25 (CH3)3 127 I I CEN 140 DMF KOH 25 128 197-198 DMF KOH CH3 129 [O 145 DMF KOH 130 m 290 DMF KOH 110 131 204 DMF K011 90 N 1 1.- gm 2% DMF K011 90 N 133 @fl 171-1715 DMF K011 90 TABLE 2-Continued No. in Constitution Melting Solvent alkali reaction sequence point metal temperature "C compound N 134 I l 1) 144-1455 DMF NuOH 90 OCH N 3 135 1 l27l28 DMF M11011 911 O o CCHa 136 N 1711-172 DMF KOH 90 CH3 137 N 193-194 DMF KOH 91 138 350 DMA NuOH 125 139 350 DMA NuOH 125 140 350 DMA NuOH I25 (CH C 141 350 HMPT KO-tcrL- I25 Butylul TABLE 2-Continued N0. in (onstitution Melting Solvent alkali reaction sequence point metal temperature C compound "C 142 l l 350 DMA KOH 120 143 350 DMF KOH 120 I44 I I 121 HMPT KOH 80 DMF dimcthyl formamide DEF dicthyl formamide DMA dimethyl ucetarnidc HMPT hexamethyl-phosphoric acid trisamide.

I claim: 2. A compound as defined in claim 1, wherein A is l. A compound of the formula in which A, R and E are as defined above.

E is phenyl or chlorophenyl. i

4. A compound as defined in claim 1, wherein R is hydrogen and E is phenyl.

5 The compound as defined in claim 1, wherein A is phenyl, R is hydrogen, E is phenyl and D is 

1. A COMPOUND OF THE FORMULA
 2. A compound as defined in claim 1, wherein A is phenyl, mono-or di-(lower alkyl)-phenyl, indanyl, tetrahydronaphthyl or naphthyl; R is hydrogen or methyl; E is phenyl or chlorophenyl.
 3. A compound as defined in claim 1, wherein A is phenyl, tolyl, xylyl, tert.-butyl phenyl, indanyl or naphthyl, R is hydrogen or methyl, E is phenyl or chlorophenyl.
 4. A compound as defined in claim 1, wherein R is hydrogen and E is phenyl.
 5. The compound as defined in claim 1, wherein A is phenyl, R is hydrogen, E is phenyl and D'' is 